page_title: Extinct comet
section_title: Nature of extinct comets
hierarchical_section_title: Extinct comet / Nature of extinct comets
caption_attribution_description: English: March 6, 2014 RELEASE 14-060 NASA's Hubble Telescope Witnesses Asteroid's Mysterious Disintegration http://www.nasa.gov/press/2014/march/nasas-hubble-telescope-witnesses-asteroids-mysterious-disintegration-1/ This series of Hubble Space Telescope images reveals the breakup of an asteroid over a period of several months starting in late 2013. The largest fragments are up to 180 meters (200 yards) in radius. NASA's Hubble Space Telescope has recorded the never-before-seen break-up of an asteroid into as many as 10 smaller pieces. Fragile comets, comprised of ice and dust, have been seen falling apart as they near the sun, but nothing like this has ever before been observed in the asteroid belt. "This is a rock, and seeing it fall apart before our eyes is pretty amazing," said David Jewitt of the University of California at Los Angeles, who led the astronomical forensics investigation. The crumbling asteroid, designated P/2013 R3, was first noticed as an unusual, fuzzy-looking object by the Catalina and Pan STARRS sky surveys on Sept. 15, 2013. A follow-up observation on October 1 with the W. M. Keck Observatory on the summit of Mauna Kea, a dormant volcano on the island of Hawaii, revealed three bodies moving together in an envelope of dust nearly the diameter of Earth. "The Keck Observatory showed us this thing was worth looking at with Hubble," Jewitt said. "With its superior resolution, space telescope observations soon showed there were really 10 embedded objects, each with comet-like dust tails. The four largest rocky fragments are up to 400 yards in diameter, about four times the length of a football field." Hubble data showed the fragments drifting away from each other at a leisurely one mph. The asteroid began coming apart early last year, but new pieces continue to reveal themselves, as proved in the most recent images. It is unlikely the asteroid is disintegrating because of a collision with another asteroid, which would have been instantaneous and violent by comparison to what has been observed. Debris from such a high-velocity smashup would also be expected to travel much faster than observed. Nor is the asteroid coming unglued due to the pressure of interior ices warming and vaporizing. This leaves a scenario in which the asteroid is disintegrating due to a subtle effect of sunlight, which causes the rotation rate of the asteroid to gradually increase. Eventually, its component pieces -- like grapes on a stem -- succumb to centrifugal force and gently pull apart. The possibility of disruption in this manner has been discussed by scientists for several years, but never reliably observed. For this scenario to occur, P/2013 R3 must have a weak, fractured interior -- probably as the result of numerous non-destructive collisions with other asteroids. Most small asteroids are thought to have been severely damaged in this way. P/2013 R3 is likely the byproduct of just such a collision sometime in the last billion years. With the previous discovery of an active asteroid spouting six tails, named P/2013 P5, astronomers are finding more evidence the pressure of sunlight may be the primary force causing the disintegration of small asteroids -- less than a mile across-- in our solar system. The asteroid's remnant debris, weighing about 200,000 tons, will in the future provide a rich source of meteoroids. Most will eventually plunge into the sun, but a small fraction of the debris may one day blaze across our skies as meteors. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington. For images and more information about Hubble, visit: http://www.nasa.gov/hubble
context_page_description: An extinct comet is a comet that has expelled most of its volatile ice and has little left to form a tail and coma. In a dormant comet, rather than being depleted, any remaining volatile components have been sealed beneath an inactive surface layer.
  Due to the near lack of a coma and tail, an extinct or dormant comet may resemble an asteroid rather than a comet and blur the distinction between these two classes of small Solar System bodies. When volatile materials such as nitrogen, water, carbon dioxide, ammonia, hydrogen and methane in the comet nucleus have evaporated away, all that remains is an inert rock or rubble pile. A comet may go through a transition phase as it comes close to extinction.
context_section_description: Extinct comets are those that have expelled most of their volatile ice and have little left to form a tail or coma.  Over time, most of the volatile material contained in a comet nucleus evaporates away, and the comet becomes a small, dark, inert lump of rock or rubble that can resemble an asteroid. 
   
  Other related types of comet include transition comets, that are close to becoming extinct, such as were looked for in the Hubble search for transition comets. Comets such as C/2001 OG108 (LONEOS) may represent the transition between extinct comets and typical Halley-type comets (periods of 20–200 years) or long period comets (periods longer than 200 years). Minor planets of the group of damocloids have been studied as possible extinct cometary candidates due to the similarity of their orbital parameters with those of Halley-type comets.
caption: Disintegration of asteroid P/2013 R3 observed by the Hubble Space Telescope between late-October 2013 and early-January 2014.[3]
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